In widely known configurations for protecting imaging lenses, barriers are provided in front of the lenses, for example, on the ends of lens-barrels such that the barriers can be opened and closed. A lens barrier unit (barrier open/close support device) including such barriers is typically configured as follows: a flat plate as a barrier is divided into an upper half serving as an upper barrier and a lower half serving as a lower barrier. These barriers are supported by a barrier support mechanism including a support arm such that the barriers can extend and retract in the vertical direction. Instead of upper and lower barriers, a barrier may be divided into right and left barriers or in a substantially diagonal direction, or three or more barriers may be provided.
In such a lens barrier unit of the related art, a lens to be protected by the barriers typically has a spherical surface but the barriers are flat. Thus a distance between the barrier and the lens increases on the outer periphery of the lens surface and results in a large space. Consequently, a lens-barrel including the lens barrier unit increases in capacity, which has been an obstacle to size reduction.
Further, in the lens barrier unit of the related art, the flat barriers require retraction spaces directly above and below an opening that is opened and closed by the barriers. The spaces directly above and below the opening cannot be effectively used for other functional components or cannot be eliminated for size reduction.
In order to address this problem, Japanese Patent Laid-Open No. 2002-258133 (hereinafter, will be called patent document 1) discloses a lens-barrel having spherical barriers along the surface of a lens instead of flat barriers. As shown in FIG. 16, a barrier 11 of the lens-barrel has a spherical surface (called a partially spherical shell in patent document 1) centered around a point on the axis of the lens-barrel (the optical axis of the lens). The barrier 11 is divided into an upper half barrier 12 and a lower half barrier 13. The upper half barrier 12 and the lower half barrier 13 are supported by two pairs of arms 14L, 14R, 15L, and 15R that extend from both sides to the rears of the barriers. Further, the upper half barrier 12 and the lower half barrier 13 can pivot about a pivotal axis 18 passing through two pivot shafts 16 and 17 provided at the rear ends of the arms 14L, 14R, 15L, and 15R. The pivotal axis 18 is orthogonal to the axis of the lens-barrel (the optical axis of the lens). Thus the upper half barrier 12 and the lower half barrier 13 can vertically open and close in a movement path that is substantially shaped like a cylinder centered around the pivotal axis 18 and has a radius between the pivotal axis 18 and the upper half barrier 12 (or the lower half barrier 13).
In the case of the spherical barrier 11, a distance between the barrier 11 and the lens does not vary between the outer periphery and the center of the lens, thereby reducing a distance between the outer periphery of the lens surface and the barrier 11. Thus the lens-barrel including the lens barrier unit can be reduced in capacity, achieving size reduction to some extent. Moreover, the retracted upper half barrier 12 and lower half barrier 13 are located in the rear as compared to the upper half barrier 12 and lower half barrier 13 in a closed state. With this configuration, an area directly above the closed upper half barrier 12 and an area directly below the closed lower half barrier 13 can be effectively used for other functional components, or these areas can be eliminated from the lens barrier unit and the lens-barrel.